1. Field of the Invention
The present invention relates to a traveling wave tube and more particularly to a traveling wave tube having a delay line in the form of a spiral or ring ribbon conductor, arranged between an electron beam generating system and an electron beam collector within a sturdy metallic vacuum shell.
2. The Prior Art
Traveling wave tubes incorporating spiral-shaped delay lines supported within a sturdy metallic vacuum shell by a number of dielectric support rods are known from the German AS No. 1,937,704, which corresponds to the Gross et al U.S. Pat. No. 3,634,723. The apparatus illustrated therein incorporates a number of dielectric support rods arranged parallel to one another, which support rods are fixed in their lateral position by means of the shape of the interior cross section of the vacuum shell, with good thermal contact between the support rods and the shell. Such traveling wave tubes have a flexible support mounting of the spiral system for assisting in attaining a good heat dissipation from the spiral to the vacuum shell. It is also known from the Gross et al patent to allow the vacuum shell, when it is constructed of glass, to expand through heating and thereafter to shrink onto the support rods so that its interior cross section assumes longitudinal grooves which support the longitudinal support rods. The Gross et al patent also describes that the spiral may be soldered together with the support rods and the rods are in turn soldered to the vacuum shell for the purpose of rendering the spiral insensitive to vibration. When this is attempted during manufacture, however, it becomes clear that a complicated manufacturing arrangement is required, and also, the completed construction can suffer cracks in either the solder joints or the ceramic support rods, due to thermal expansion. As a result, the previously known design is not suitable for construction of traveling wave tubes with relatively small dimensions, or with relatively high power capacities which require the dissipation of considerable quantities of heat.